Lawrence Berkeley National Laboratory has announced and published methods and systems for direct colorimetric detection of receptor-ligand interaction using a polymerized bilayer sensor. The sensor comprises a plurality of sensor molecules fabricated into a thin film. Each sensor molecule includes a molecular receptor which binds to a molecule of interest, such as E. coli 0157:H7. The backbone of the sensor molecule includes a colorimetric detection element in the form of a long diacetylene lipid. Exposure to ultraviolet light links the molecular receptor with the colorimetric detection element by activating a triple bond within the diacetylene lipids. A blue-tinted polydiacetylene (PDA) film results from this step.
The PDA film is sensitive to changes on its surface as manifested by the wavelength of light transmitted thereby. For example, when E. coli 0157:H7 toxins bind to the surface of the sensor, the backbone chain of PDA reorganizes to produce a red tint. The colorimetric reaction from blue to red is visible by a naked eye.
In another application, a synthetic membrane based on polydiacetylenes is formed to have influenza virus binding sites on its surface. The color of the membrane changes from blue to red in response to a binding event of a sample of influenza virus to the binding sites.